Dense line extreme ultraviolet lithography system with distortion matching

ABSTRACT

An extreme ultraviolet lithography system ( 10 ) that creates a new pattern ( 330 ) having a plurality of densely packed parallel lines ( 332 ) on a workpiece ( 22 ), the system ( 10 ) includes a patterning element ( 16 ); an EUV illumination system ( 12 ) that directs an extreme ultraviolet beam ( 13 B) at the patterning element ( 16 ); a projection optical assembly ( 18 ) that directs the extreme ultraviolet beam diffracted off of the patterning element ( 16 ) at the workpiece ( 22 ) to create a first stripe ( 364 ) of generally parallel lines ( 332 ) during a first scan ( 365 ); and a control system ( 24 ). The workpiece ( 22 ) includes an existing pattern ( 233 ) that is distorted. The control system ( 24 ) selectively adjusts a control parameter during the first scan ( 365 ) so that the first stripe ( 364 ) is distorted to more accurately overlay the portion of existing pattern ( 233 ) positioned under the first stripe ( 364 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from each and every one of thefollowing U.S. Provisional patent application Ser. No. 62/352,545 filedon Jun. 20, 2016 and titled “Dense Line Extreme Ultraviolet LithographySystem with Distortion Matching”; Ser. No. 62/353,245 filed on Jun. 22,2016 and titled “Extreme Ultraviolet Lithography System that UtilizesPattern Stitching”; and Ser. No. 62/504,908 filed on May 11, 2017 andtitled “Illumination System with Curved 1D-Patterned Mask for Use inEUV-Exposure Tool”. As far as permitted, the contents of U.S.Provisional patent application Ser. No. 62/352,545, Ser. No. 62/353,245,and Ser. No. 62/504,908 are each incorporated by reference herein forall purposes.

The present application also claims priority on U.S. patent applicationSer. No. 15/599,148, filed on May 18, 2017, and titled “EUV LithographySystem for Dense Line Patterning”. Further, the present application alsoclaims priority on U.S. patent application Ser. No. 15/599,197, filed onMay 18, 2017, and titled “EUV Lithography System for Dense LinePatterning”. As far as permitted, the contents of U.S. patentapplication Ser. No. 15/599,148, and U.S. patent application Ser. No.15/599,197 are each incorporated by reference herein for all purposes.

As far as permitted, the contents of U.S. Provisional patent applicationSer. No. 62/338,893 filed on May 19, 2016 and titled “EUV LithographySystem for Dense Line Patterning”; Ser. No. 62/487,245 filed on Apr. 19,2017 and titled “Optical Objective for Dense Line Patterning in EUVSpectral Region”; and Ser. No. 62/490,313 filed on Apr. 26, 2017 andtitled “Illumination System With Flat 1D-Patterned Mask for Use inEUV-Exposure Tool” are each incorporated by reference herein for allpurposes.

TECHNICAL FIELD

The present invention relates to exposure tools used in lithographicprocessing of semiconductor workpieces, and more particularly, to anexposure tool configured to form, on a workpiece, a pattern of parallellines that are separated from one another by a few tens of nanometers orless.

BACKGROUND

Lithography systems are commonly used to transfer images from apatterning element onto a workpiece during exposure. Next generationlithography technology may use extreme ultraviolet (EUV) lithography toenable semiconductor workpieces with extremely small feature sizes to befabricated.

SUMMARY

One embodiment is directed to an extreme ultraviolet lithography systemthat creates a new pattern having a plurality of densely packed parallellines on a workpiece (e.g., a semiconductor wafer) that includes anexisting pattern that is distorted. The lithography system includes apatterning element having a patterning element pattern; a workpiecestage mover assembly that retains and moves the workpiece relative tothe patterning element; an EUV illumination system that directs anextreme ultraviolet beam (e.g., light with a wavelength of approximately13.5 nm) at the patterning element; a projection optical assembly thatdirects the extreme ultraviolet beam diffracted off of the patterningelement at the workpiece to create a first stripe of densely packedparallel lines on the workpiece that extend generally along a firstaxis; and a control system that controls the stage assembly to move theworkpiece relative to the exposure field along a first scan trajectorythat is generally parallel to the first axis during the first scan. Asprovided herein, the control system selectively adjusts a controlparameter during the first scan so that the first stripe of parallellines more accurately overlays the portion of existing patternpositioned under the first stripe of parallel lines relative to if thecontrol parameter is not adjusted.

In one embodiment, the control parameter includes selectively adjustingthe first scan trajectory to include some movement along a second axisthat is orthogonal to the first axis, and some movement about a thirdaxis that is orthogonal to the first and second axes during the firstscan so that the first stripe of parallel lines more accurately overlaysthe portion of existing pattern positioned under the first stripe ofparallel lines. During the first scan, the movement along the secondaxis and about the third axis is a function of a workpiece position ofthe stage along the first axis.

Additionally or alternatively, the control parameter can includeselectively adjusting a magnification of the patterning element patternimage during the first scan so that the first stripe of parallel linesmore accurately overlays the portion of existing pattern positionedunder the first stripe of parallel lines. Further, the control parametercan include selectively adjusting a magnification tilt (i.e., a linearvariation in magnification across the exposure field) of the patterningelement pattern image during the first scan so that the first stripe ofparallel lines more properly overlays the portion of existing patternpositioned under the first stripe of parallel lines.

In one embodiment, the existing pattern includes a plurality ofpreviously patterned dies (also called exposure “shots” or “fields,” aseach shot may contain more than one pattern or semiconductor device),and the control system controls the EUV illumination system so thatevery other die along the first scan trajectory is not exposed duringthe first scan. Subsequently, the control system can control the EUVillumination system to expose the unexposed dies along the first scantrajectory during a second scan.

In another embodiment, the control system controls the EUV illuminationsystem to stop the first scan at an interface of adjacent dies and resetthe first scan trajectory.

As provided herein, the control system can selectively adjust the firstscan trajectory and a pitch of the parallel lines transferred to theworkpiece during the first scan so that the first stripe of parallellines are distorted to more accurately overlay the portion of existingpattern positioned under the first stripe of parallel lines.

Yet another embodiment is directed to a method for transferring a newpattern having a plurality of densely packed lines onto a workpiece thatincludes an existing pattern that is distorted. The method can include(i) providing a patterning element having a patterning element pattern;(ii) moving the workpiece with a workpiece stage mover assembly;directing an extreme ultraviolet beam at the patterning element with anEUV illumination system; (iii) directing the extreme ultraviolet beamdiffracted off of the patterning element at the workpiece with aprojection optical assembly to create the plurality of densely packedparallel lines on the workpiece when the workpiece is moved relative tothe exposure field during a first scan, the first stripe of parallellines extending generally along a first axis; and (iv) controlling thestage assembly with a control system to move the workpiece relative tothe exposure field along a first scan trajectory that is generallyparallel to the first axis during the first scan; the control systemincluding a processor; wherein the control system selectively adjusts acontrol parameter during the first scan so that the first stripe ofparallel lines more accurately overlays the portion of existing patternpositioned under the first stripe of parallel lines.

An embodiment is also directed to a device manufactured with thelithography system, and/or a workpiece (e.g., a semiconductor wafer) onwhich an image has been formed by the lithography system.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of this invention, as well as the invention itself,both as to its structure and its operation, will be best understood fromthe accompanying drawings, taken in conjunction with the accompanyingdescription, in which similar reference characters refer to similarparts, and in which:

FIG. 1A is a simplified, schematic view illustrating an extremeultraviolet lithography system having features of the presentembodiment;

FIG. 1B is a simplified side view of a shutter assembly having featuresof the present embodiment;

FIG. 2A is a simplified top view of a workpiece that has been processedto include an existing pattern;

FIG. 2B is a simplified graph illustrating raw, broad distortion datafor a workpiece processed with a step and repeat or step and scanlithography system;

FIG. 2C is a simplified graph illustrating only the global distortiondata for the workpiece;

FIG. 2D is a simplified graph illustrating the distortion data for eachdie of the workpiece;

FIG. 2E includes a graph that illustrates the common distortion shape ofthe dies;

FIG. 2F includes a graph that illustrates residual distortion data;

FIG. 3A is a flow chart illustrating a procedure having features of thepresent embodiment;

FIG. 3B is a simplified top view of a workpiece including a first stripeof parallel lines;

FIG. 3C is a simplified top view of a workpiece including the firststripe of parallel lines and a second stripe of parallel lines;

FIG. 3D is simplified top view of a portion of the patterning elementpattern projected onto the workpiece;

FIG. 3E is simplified top view of another portion of the patterningelement pattern projected onto the workpiece;

FIG. 3F is simplified top view of a portion of the workpiece with aportion of a new pattern overlaying an existing pattern;

FIG. 4A is a simplified top view of the workpiece with a first portionof the first stripe of parallel lines;

FIG. 4B is a simplified top view of the workpiece with a second portionof the first stripe of parallel lines;

FIG. 4C is simplified top view of the workpiece and yet another firststripe of parallel lines;

FIG. 5A is a flow chart that outlines a process for manufacturing adevice in accordance with the present embodiment; and

FIG. 5B is a flow chart that outlines device processing in more detail.

DESCRIPTION

FIG. 1A is a simplified, non-exclusive, schematic view illustrating anextreme ultraviolet (EUV) lithography system 10 that includes an EUVillumination system 12 (irradiation apparatus) that generates an initialEUV beam 13A (illustrated with dashed lines), a patterning element stageassembly 14 that retains a patterning element 16 having a patterningelement pattern 16A, a projection optical assembly 18, a workpiece stageassembly 20 that retains and positions a workpiece 22, which can be asemiconductor wafer, a control system 24 that controls the operation ofthe components of the system 10, and a shutter assembly 26 that definesthe shape of an exposure field 28 on the workpiece 22 created with ashaped and diffracted EUV beam 13D, 13E. The design and location ofthese components can be varied pursuant to the teachings providedherein.

Additionally, it should be noted that the EUV lithography system 10 willtypically include more components than illustrated in FIG. 1A. Forexample, the EUV lithography system 10 can include a rigid apparatusframe (not shown) for retaining one or more of the components of thesystem. Moreover, the EUV lithography system 10 can include one or moretemperature control systems (not shown) that control the temperature ofone or more of the components of the EUV lithography system 10. Forexample, the EUV illumination system 12, the patterning element 16, theprojection optical assembly 18, and/or the workpiece stage assembly 20can require cooling with a temperature control system.

Additionally, for example, the EUV system 10 can include an enclosedchamber 29 that allows for many of the components of the EUV lithographysystem 10 to operate in a controlled environment, such as a vacuum.

As an overview, the EUV lithography system 10 directs the exposure field28 onto the workpiece 22 that is being moved along a scan trajectory totransfer a new pattern 330 (illustrated in FIG. 3B) that only includes aplurality of densely packed, generally parallel lines 332 onto thesemiconductor workpiece 22 which already includes an existing pattern233 (illustrated in FIG. 2A). In certain embodiments, the EUVlithography system 10 adjusts one or more control parameters, such asthe scan trajectory of the workpiece 22, a magnification of the image ofpatterning element pattern 16A, and/or a magnification tilt of image ofthe patterning element pattern 16A while scanning and exposing theworkpiece 22 so that the new pattern 233 follows and more closelyoverlays the existing pattern 233 than if one or more of the controlparameter was not adjusted. Thus, in one embodiment, present embodimentcreates an imperfect new pattern 330 of densely packed, generallyparallel lines to better match and better overlay the distorted existingpattern 233. Further, in certain embodiments, the EUV lithography system10 can be controlled to create discontinuities between adjacent diesalong the scan trajectory. More specifically, the EUV lithography system10 can be controlled to scan every stripe of parallel lines on theworkpiece 22 twice, exposing every other die in the first pass, and thealternate dies in the second pass.

In summary, the EUV lithography system 10 is uniquely designed to moreaccurately match and overlay a new pattern 330 of lines to a distortedexisting pattern 233 on the workpiece 22 by adjusting the scantrajectory, magnification, and “magnification tilt” of the patterningelement pattern 16A while scanning and exposing the workpiece 22.Because of workpiece distortion and the characteristics of how thelayers of the existing pattern 233 were created, the existing pattern istypically distorted. With the present embodiment, the new patterningelement pattern 330 is printed to be distorted in a more closelymatching fashion.

Some of the Figures provided herein include an orientation system thatdesignates the X axis, the Y axis, and a Z axis that are orthogonal toeach other. In these Figures, the Z axis is oriented in the verticaldirection. It should be understood that the orientation system is merelyfor reference and can be varied. For example, the X axis can be switchedwith the Y axis and/or the EUV lithography system 10 can be rotated.Moreover, these axes can alternatively be referred to as the first, thesecond, or a third axis. For example, the Y axis can be referred to asthe first axis, the X axis can be referred to as the second axis, andthe Z axis can be referred to as the third axis.

The EUV illumination system 12 includes an EUV illumination source 34and an illumination optical assembly 36. The EUV illumination source 34emits the initial EUV beam 13A and the illumination optical assembly 36directs and conditions the EUV beam 13A from the illumination source 34to provide an adjusted EUV beam 13C that is directed at the patterningelement 16. In FIG. 1A, the EUV illumination system 12 includes a singleEUV illumination source 34 and a single illumination optical assembly36. Alternatively, the EUV illumination system 12 could be designed toinclude a multiple EUV illumination sources 34 and multiple illuminationoptical assemblies 36.

As provided herein, the EUV illumination source 34 emits the EUV beam13A that is within the EUV spectral range. As provided herein, the “EUVspectral range” shall mean and include wavelengths between approximatelyfive and fifteen nanometers, and preferably within a narrow band around13.5 nanometers. As a non-exclusive example, the EUV illumination source34 can be a plasma system, such as either a Laser Produced Plasma (LPP)or a Discharge Produced Plasma (DPP).

The illumination optical assembly 36 is reflective, and includes one ormore optical elements that are operable in the EUV spectral range. Morespecifically, each optical element includes a working surface that iscoated to reflect light in the EUV spectral range. Further, the opticalelements are spaced apart from each other.

In FIG. 1A, the illumination optical assembly 36 includes a firstillumination optical element 38, a second illumination optical element40, and a third illumination optical element 42 that cooperate tocondition the initial EUV beam 13A and direct the conditioned EUV beam13C at the patterning element 16. In one embodiment, the firstillumination optical element 38 is a fly's eye type reflector thatincludes a plurality of individual, micro-reflectors (micro-mirrors orfacets) that are arranged in a two dimensional array, with eachreflector including a working surface that is coated to reflect light inthe EUV spectral range. Similarly, the second illumination opticalelement 40 is a fly's eye type reflector that includes a plurality ofindividual, micro-reflectors (micro-mirrors or facets) that are arrangedin a two dimensional array, with each reflector including a workingsurface that is coated to reflect light in the EUV spectral range.Further, the third illumination optical element 42 is a reflector thatincludes a working surface that is coated to reflect light in the EUVspectral range. In certain embodiments, the illumination opticalelements 38, 40, 42 comprise curved surfaces for focusing the EUV light.

In FIG. 1A, the EUV illumination source 34 emits the initial EUV beam13A generally downward at the first illumination optical element 38. Theplurality of micro-reflectors of the first illumination optical element38 reflect and redirect the EUV beam generally upward at the secondillumination optical element 40. Somewhat similarly, the plurality ofmicro-reflectors of the second illumination optical element 40 reflectand redirect the EUV beam generally downward at the third illuminationoptical element 42. Next, the third illumination optical element 42 actsas a relay that collects, reflects, and uniformly focuses theconditioned EUV beam 13C generally upward onto a patterning elementsurface 16A of the patterning element 16. It should be noted that thefaceted mirror surfaces of the first illumination optical element 38form images of the EUV illumination source 34 at each of the facetedmirror surfaces of the second illumination optical element 40. Inresponse, the faceted mirror surfaces of the second illumination opticalelement 40 reflect a uniform image of the first illumination opticalelement 38 via the third illumination optical element 42 onto thepatterning element 16. In the embodiment shown, an intermediate image ofthe first illumination optical element 38 is formed at intermediateimage plane 56 between illumination optical element 40 and illuminationoptical element 42. Stated in another fashion, each facet of the secondillumination optical element 40 is optically conjugate to the EUV source34 and the third illumination element 42, while each facet of firstillumination optical element 38 is optically conjugate to theintermediate image plane 56 and the patterning element 16. With thisarrangement, the image field of each reflector surface of the firstillumination optical element 38 overlaps at the patterning element 16 toform a sufficiently uniform irradiance pattern on the patterning element16.

The patterning element stage assembly 14 holds the patterning element16. In certain embodiments, the patterning element stage assembly 14 canbe designed to make slight adjustments to the position and/or shape ofthe patterning element 16 to improve the imaging performance of the EUVlithography system 10. For example, in certain embodiments, thepatterning element stage assembly 14 can shape, position and/or move thepatterning element 16 to make changes and adjustments to a magnificationof the exposure field 28, and changes to a magnification tilt of theexposure field 28. In one non-exclusive example, the patterning elementstage assembly 14 can include a patterning element stage 14A, and apatterning element stage mover 14B. In the non-exclusive embodimentillustrated in FIG. 1A, the patterning element stage 14A is monolithicand includes a patterning element holder (not shown) that retains thepatterning element 16. For example, the patterning element holder can bean electrostatic chuck or some other type of clamp.

The patterning element stage mover 14B controls and adjusts the positionof the patterning element stage 14A and the patterning element 16. Forexample, the patterning element stage mover 14B can move and position ofthe patterning element 16 with six degrees of freedom, e.g. along the X,Y, and Z axes, and about the X, Y, and Z axes. Alternatively, thepatterning element stage mover 14B can be designed to move thepatterning element 16 with less than six degrees of freedom, e.g. withthree degrees of freedom. Further, in certain embodiments, thepatterning element stage mover 14B and/or the patterning element holdercan be controlled by the control system 24 to distort the patterningelement 16 by stretching, bending, or compressing the patterning element16 as needed. As provided herein, the patterning element stage mover 14Bcan include one or more piezoelectric actuators, planar motors, linearmotors, voice coil motors, attraction only actuators, and/or other typesof actuators. In certain embodiments, the range of motion of thepatterning element stage 14A is relatively small.

The patterning element 16 diffracts the conditioned EUV beam 13C tocreate an image projected onto the workpiece 22. For example, thepatterning element 16 can be a diffraction grating. In one embodiment,the patterning element pattern 16A of the patterning element 16 includesa periodic structure that reflects and diffracts the conditioned EUVbeam 13C in multiple directions, including a first diffracted EUV beam13D and a second diffracted EUV beam 13E that travel in differentdirections away from the patterning element 16. In one embodiment, theperiodic structure of the patterning element 16 includes a pattern ofparallel lines that are parallel to the Y axis. In an alternativeembodiment, the patterning element 16 may be a periodic structure thatalters the phase and/or the intensity of the EUV beam 13C. For example,the periodic structure may be a pattern of reflective and non-reflectivelines at an appropriate pitch to create the desired diffracted beams.Alternatively, the periodic structure may be a pattern of lines thatvary the optical phase of the EUV light to create the desired diffractedbeams.

The projection optical assembly 18 directs the diffracted EUV beams 13D,13E to form an image of the patterning element 16 onto a light-sensitivephotoresist material on the semiconductor workpiece 22 positioned at animage plane of the projection optical assembly 18. In one embodiment,the projection optical assembly 18 is reflective and includes one ormore optical elements that are operable in the EUV spectral range. Morespecifically, each optical element includes a working surface that iscoated to reflect light in the EUV spectral range. Further, the opticalelements are spaced apart from each other.

In FIG. 1A, the projection optical assembly 18 directs EUV lightreflected from the patterning element 16, including the first diffractedEUV beam 13D and the second diffracted EUV beam 13E at the workpiece 22.Stated in another fashion, with the present embodiment, light wavesdiffracted or scattered from the patterning element 16 are collected bythe projection optical assembly 18 and recombined to produce the imageof the patterning element 16 on the workpiece 22. Because the patterningelement 16 that scatters/diffracts the EUV beam is imaged onto theworkpiece 22, the edges appear as sharp boundaries in the resist of theworkpiece 22. Thus, one of the significant advantages of the projectionoptical system 18 is that it allows for well-defined edges to theexposure field 28. In FIG. 1A, the projection optical assembly 18includes a first projection subassembly 44 and a second projectionsubassembly 46 that cooperate to form the image of the patterningelement pattern on the workpiece 22. In contrast, if the projectionoptical system 18 merely directs the two diffracted EUV beams 13D, 13Eto form an interference pattern on the workpiece 22, the edges willappear out of focus and blurred.

For example, (i) the first projection subassembly 44 can include a left,first projection optical element 44A, and a right, first projectionoptical element 44B that cooperate to direct the reflected EUV light;and (ii) the second projection subassembly 46 can include a left, secondprojection optical element 46A, and a right, second projection opticalelement 46B that cooperate to direct the reflected EUV light. In oneembodiment, each first projection optical element 44A, 44B is areflector that includes a working surface that is coated to reflectlight in the EUV spectral range. Similarly, each second projectionoptical element 46A, 46B is a reflector that includes a working surfacethat is coated to reflect light in the EUV spectral range. In certainembodiments, optical elements 44A, 44B are formed as portions of asingle EUV mirror. Similarly, optical elements 46A, 46B may be formed asportions of a single EUV mirror. Depending on the particularapplication, optical elements 44A, 44B may be two portions of a singlecurved mirror, or they may be separate components. Similarly, opticalelements 46A, 46B may be two portions of a single curved mirror, or theymay be separate components.

The workpiece stage assembly 20 holds the workpiece 22, positions andmoves the workpiece 22 relative to the exposure field 28 to create thepattern 330 of parallel lines which are densely packed on the workpiece22. As one non-exclusive example, the workpiece stage assembly 20 canincludes a workpiece stage 48, and a workpiece stage mover 50(illustrated as a box).

In the non-exclusive embodiment illustrated in FIG. 1A, the workpiecestage 48 is monolithic and includes a workpiece holder (not shown) thatretains the workpiece 22. For example, the workpiece holder can be anelectrostatic chuck or some other type of clamp.

The workpiece stage mover 50 controls and adjusts the position of theworkpiece stage 48 and the workpiece 22 relative to the exposure field28 and the rest of the EUV lithography system 10. For example, theworkpiece stage mover 50 can move and position of the workpiece 22 withsix degrees of freedom, e.g. along the X, Y, and Z axes, and about theX, Y, and Z axes. Alternatively, the workpiece stage mover 50 can bedesigned to move the workpiece 22 with less than six degrees of freedom,e.g. with three degrees of freedom. As provided herein, the workpiecestage mover 50 can include one or more planar motors, linear motors,voice coil motors, attraction only actuators, and/or other types ofactuators.

In certain embodiments, the scanning velocity can be varied according tothe size of the exposure field 28. Further, in certain embodiments, theworkpiece stage mover 50 moves the workpiece 22 at a substantiallyconstant velocity during each scanning processes.

The control system 24 is electrically connected and directs and controls(i) electrical current to the workpiece stage assembly 20 to control theposition of the workpiece 22; (ii) electrical current to the patterningelement stage assembly 14 to control the position and/or shape of thepatterning element 16; (iii) the EUV illumination system 12 to controlthe EUV beam 13; and (iv) the shutter assembly 26 to adjust the shape ofthe exposure field 28. The control system 24 can include one or moreprocessors 54, and electronic data storage.

The shutter assembly 26 shapes the EUV beam 13A and defines the shape ofthe exposure field 28 imaged on the workpiece 22. In one, non-exclusiveembodiment, the shutter assembly 26 shapes the EUV beam so that theexposure field 28 has a generally rectangular shape.

FIG. 1B is a simplified side view of a non-exclusive example of theshutter assembly 26. In this embodiment, the shutter assembly 26includes a rigid shutter housing 26A that defines a housing opening 26B(illustrated with dashed lines), a movable shutter 26C (illustrated witha box), and a shutter mover 26D (illustrated with a box). In thisembodiment, the housing opening 26B defines generally the shape and sizeof the exposure field 28 (illustrated in FIG. 1A). However, in thisembodiment, the movable shutter 26C can be selectively moved by theshutter mover 26D relative to the housing opening 26B to selectivelycover a portion, cover all, or not cover the housing opening 26B toadjust the size of the exposure field 28 along the Y axis (illustratedin FIG. 1A).

In FIG. 1B, the movable shutter 26C includes a shutter opening 26E. Withthis design, the movable shutter 26 can be moved back and forth toselectively and alternatively adjust the size of the exposure field 28from either direction along the Y axis (the scan direction).

Further, the shutter mover 26D can be a motor that is controlled by thecontrol system 24 (illustrated in FIG. 1A) to selectively andalternatively adjust the size of the exposure field 28 from eitherdirection along the Y axis during the scanning process, depending uponthe scan direction. In alternative embodiments, the shutter assembly 26may include additional actuators or moving parts to allow modificationsof the shape of the exposure field 28 to correct for non-uniformity ofthe EUV illumination or other effects.

With reference back to FIG. 1A, the shutter assembly 26 can bepositioned in a number of different locations along a beam path 55between the EUV illumination source 34 and the workpiece 22. Forexample, the shutter assembly 26 can be positioned along the beam path55 (i) in proximity to the patterning element 16, (ii) in proximity tothe workpiece 22, or (iii) at or near an intermediate image plane. Inthe embodiment illustrated in FIG. 1A, the shutter assembly 26 ispositioned along the beam path 55 at intermediate image plane 56 betweenthe second illumination optical element 40 and the third illuminationoptical element 42. As a result thereof, the conditioned EUV beam 13Cdirected at the patterning element 16 is already shaped. In alternativeembodiments that have an intermediate image plane at another location,such as between the patterning element 16 and the workpiece 22, thepattern shutter 26 can be positioned along the beam path 55 at thatintermediate image plane (not shown).

It should be noted that any of EUV beams 13A, 13C, 13D, 13E can bereferred to generally as an EUV beam. Further, as used herein, the termbeam path 55 shall refer to the path that the EUV beam travels from theillumination source 34 to the workpiece 22.

FIG. 2A is a simplified top view of a workpiece 22 that has beenprocessed to include the existing pattern 233 (only a portion isillustrated as small circles) having a plurality of adjacent dies 260(also referred to as “exposure shots”, “shots”, or “chips”) on theworkpiece 22. The design of the existing pattern 233, and the number,size and shape of the dies 260 can be varied. In the non-exclusiveexample illustrated in FIG. 2A, the workpiece 22 has been processed toinclude ninety-six rectangular shaped dies 260. Further, for a threehundred millimeter diameter workpiece 22, each of the dies 260 can be,for example, twenty-six millimeters (along the X axis) by thirty-threemillimeters (along the Y axis). However, other numbers and other sizesare possible. A center of each die 260 is identified with a plus sign.Each die 260 can be created on the workpiece 22 using a step and repeatlithography system or a step and scan lithography system (not shown)that exposes an area on the workpiece 22 to create one of the dies 260and subsequently stepped to another area to create another die 260. Thisprocess is repeated until the entire existing pattern 233 is completed.

Unfortunately, as provided herein, the existing pattern 233 on theworkpiece 22 is often distorted. As non-exclusive examples, distortionof the existing pattern 233 can be caused by temperature changes in theworkpiece 22 during the various processing steps, residual stress in theworkpiece 22, chucking of the workpiece 22, etching of the workpiece 22,chucking of a reticle used in the step and repeat lithography system,and/or irregularities in the projection optical assembly of the step andrepeat lithography system.

FIG. 2B is a simplified graph illustrating the raw, broad distortiondata for a workpiece 22 processed with the step and repeat lithographysystem. It should be noted that the raw distortion data will bedifferent for each workpiece 22. In FIG. 2B, the distortion isrepresented by a plurality of tiny vectors (arrows) 262 at a pluralityof alternative, spaced apart locations on the workpiece 22. Thesevectors 262 illustrate how the existing pattern 233 (illustrated in FIG.2A) is distorted at those particular locations relative to a desiredpattern (not shown). Generally, the size of the vector 262 representsthe size of the distortion and the direction represents the direction ofthe distortion from their proper position.

In FIG. 2B, the X axis and Y axis dimensions of the workpiece 22 arealso illustrated for reference. In this example, the workpiece 22 has athree hundred millimeter diameter. It should be noted that for theworkpiece 22 illustrated in FIG. 2B, the distortion is the highest inthe lower right quadrant and the lowest in the upper left quadrant.

As a non-exclusive example, the distortion data can be generated byprecisely measuring the existing pattern 233 and comparing the existingpattern 233 to the desired pattern.

It should be noted that the broad distortion data illustrated in FIG. 2Bincludes two major effects, namely (i) how the workpiece 22 has beenglobally stretched or distorted, and (ii) how each of the dies 260 isdistorted.

FIG. 2C is a simplified graph illustrating only the global distortiondata (with small arrows) for that workpiece 22. Stated in anotherfashion, FIG. 2C is a linear fit of the data that illustrates how thewhole workpiece 22 is distorted. This can also be referred to asinter-shot distortion data or workpiece distortion data.

It should be noted that for the workpiece 22 illustrated in FIG. 2C, theglobal distortion of the workpiece 22 is the highest in the lower rightquadrant and the lowest in the upper left quadrant.

For example, the global distortion data in FIG. 2C can be generated byfitting linear equations for the X and Y distortion components to theraw data shown in FIG. 2B.

FIG. 2D is a graph illustrating the distortion data (with small arrows)for each die 260 of that workpiece 22. It should be noted that for theworkpiece 22 illustrated in FIG. 2D, the distortion for each die 260 isapproximately the same (consistent and repetitive). This is because thedie distortion from a step and repeat or step and scan exposure processis typically caused by gravity sag of the reticle used during exposure(not shown), temperature fluctuations of the reticle, distortion of thereticle caused by chucking, and distortion characteristics of theprojection lens assembly of the lithography system. The die distortioncan also be referred to as intra-shot distortion data.

It should be noted that the die distortion data can be calculated bysubtracting the workpiece distortion data from FIG. 2C from the broad,overall distortion data from FIG. 2B.

FIG. 2E shows a graph that was generated using the die distortion datafrom FIG. 2D to estimate the common distortion shape for each of theninety-six dies 260. In FIG. 2E, the graph illustrates the commondistortion shape for each die generated using linear polynomialequations (first order correction).

FIG. 2F illustrates the residual distortion data. More specifically, theresidual distortion data illustrated in FIG. 2F is obtained bysubtracting the graph of FIG. 2E from the die distortion data of FIG.2D.

FIG. 3A is a simplified flow chart that illustrates the steps taken forthe new pattern 330 generated by the EUV lithography system 10 of FIG.1A to overlay and match the existing pattern 233. More specifically, atblock 300, the distortion data of the existing pattern on the workpieceis determined. Once the distortion data for the workpiece is determined,one or more control parameters necessary for the new pattern to overlaythe existing pattern 302 are determined at block 302. Stated in anotherfashion, using the distortion data of the existing pattern 233, thedesired location and characteristics of the new pattern 330 can bedetermined so that the plurality of lines of the new pattern 330 matchesand overlays the distorted existing pattern 233. As provided herein, theone or more control parameters for each scan that creates the newpattern 330 can be determined so that the new pattern 330 overlays thedistorted existing pattern 233. Steps 300 and 302 can be performedoffline and before beginning exposure of the new pattern 330.

As a non-exclusive examples, the control parameters for the EUVlithography system 10 during the generation of the new pattern 330 caninclude adjustments to each scan trajectory (e.g. an X axis offset ofthe workpiece, a theta Z axis (θz) rotation of the workpiece), amagnification change of the patterning element pattern during one ormore scans, and/or a magnification tilt of the patterning elementpattern during one or more scans. Further, these control parameters canbe determined as a function of the X and/or Y axis position(s) of theworkpiece. Determining the desired new pattern and each of these controlparameters can be found by several potential methods: (i) fitting apolynomial or other analytical expression to the measured data; (ii)interpolating between measurement points and smoothing anydiscontinuities; (iii) solving an optimization problem that minimizesthe residual error while maintaining a trajectory that meets stagelimitations on velocity, acceleration, and jerk; and (iv) using adigital filter to smooth the trajectory.

Next, at block 304, the new pattern 330 is transferred to the workpiece22 using the control parameters. More specifically, the EUV lithographysystem 10 illustrated in FIG. 1A can be controlled to match and overlaythe new dense line pattern 330 across the entire workpiece 22 to theexisting pattern 233 by adjusting the scan trajectory, magnification,and magnification tilt of the patterning element pattern while scanningand exposing the workpiece 22 to compensate for the distortion of theworkpiece 22 during previous processing. With this design, the EUVlithography system 10 will generate and distort the new pattern 330 in amatching fashion so that it is more accurately aligned with the existingpattern 233 which is already present on the workpiece 22 than if thecontrol parameters were not adjusted.

FIG. 3B is a simplified illustration of the workpiece 22 that includes aportion of a new pattern 330 of parallel lines 332 formed with the EUVlithography system 10 of FIG. 1A. At this time, only a first stripe 364of densely packed, generally parallel lines 332 has been transferred tothe workpiece 22. However, when finished, almost the entire surface ofthe workpiece 22 will include the densely packed, generally parallellines 232. It should be noted that the X axis spacing and shape of thelines 332 is greatly exaggerated in FIG. 3B for clarity. In thisembodiment, each of the parallel lines 332 extends across the entireworkpiece 22 substantially parallel to the Y axis and orthogonal to theX axis. It should be noted that the parallel lines 332 shown in FIG. 3Bare merely illustrative. It should be understood that in one (i.e.semiconductor wafer) non-exclusive embodiment, the spacing (pitch)between adjacent parallel lines 332 may range from ten (10) to forty(40) nanometers. It should be understood, however, that this pitch rangeshould not be construed as limiting. Parallel lines 332 having a pitchsmaller than ten (10) nanometers (for example) or larger than forty (40)nanometers (for example) can be patterned onto a workpiece 22 using theEUVL tool 10. In alternative, non-exclusive examples, the adjacentparallel lines 332 can have a pitch of less than seventy, sixty, fifty,forty, thirty, twenty, ten or five nanometers. Furthermore, as usedherein, the phrase “densely packed” means a substantially continuouspattern of lines. While in most cases the densely packed lines willcover substantially an entire workpiece surface, this is by no means arequirement. In alternative embodiments, the parallel lines may haveperiodic gaps and/or variations in pitch.

FIG. 3B also illustrates the rectangular shaped exposure field 28created by the EUV lithography system 10 of FIG. 1A on the workpiece 22.In this example, the first stripe 364 of parallel lines 332 weretransferred to the workpiece 22 during a first scan 365 of the workpiece22 relative to the exposure field 28. In the first scan 365, the stagemover 50 (illustrated in FIG. 1A) is controlled to move the workpiece 22(downward on the page in FIG. 3B) relative to the exposure field 28along a first scan trajectory 366 (illustrated with a thicker, dashedline) to create the first stripe 364 of parallel lines 332. In FIG. 3B,the first scan trajectory 366 is jagged shaped and extends generallyparallel to the Y axis. More specifically, in the first scan, the firstscan trajectory 366 is generally along the Y axis, but includes somemovement along the X axis, and about the Z axis so that the new pattern330 matches the existing pattern 233. As provided herein, the movementof the workpiece 22 during the first scan along the X axis and about theZ axis can be a function of the position of the workpiece 22 along the Yaxis.

Additionally, as provided herein, the magnification of the patterningelement pattern 16A (illustrated in FIG. 1A) and the magnification ofthe patterning element tilt of the patterning element pattern 16A can bevaried during the first scan 365 so that the new pattern 330 closelyoverlays the existing pattern 233. For example, in certain embodiments,adjusting the focus position of the patterning element 16 (illustratedin FIG. 1A) or the workpiece 22 will create a magnification change ofthe parallel lines 332. Using this effect, the patterning element 16and/or workpiece 22 can be moved slightly in the focus direction to makesmall changes in the pitch of the printed lines 332. Moreover, bytilting the patterning element 16 and/or the workpiece 22 slightly aboutthe Y axis, a “magnification tilt” can be created where the printedpitch changes linearly across the exposure field 28 in the X direction.

Further, in FIG. 3B, the first stripe 364 includes eight, spaced apartlines that are merely representative of a very large number (e.g.,millions) of densely packed lines that were printed onto the workpiece22 during the single scan along the first scan trajectory 366. In oneembodiment, the width of the first stripe 364 of lines 332 (and theexposure field 328 on the workpiece 22) can be several millimeters wide.For example, the width of the exposure field 328 can be approximatelyfive millimeters wide. As alternative, non-exclusive examples, thespacing (pitch) between adjacent parallel lines 232 can be less thanapproximately 5, 10, 20, 30, 40, 50, 60, or 70 nanometers. As providedherein, “densely packed” means a substantially continuous pattern oflines without any gaps or significant variations in the spacing.

As illustrated in FIG. 3B, in certain embodiments, during the printingof the continuous first stripe 364 with the EUV lithography system 10across the workpiece 22, it is necessary to make relatively sharpchanges to the first scan trajectory 366 at each boundary 367A (one ishighlighted with a dashed oval) of adjacent dies 260 (illustrated inFIG. 2A). Stated in another fashion, during the first scan 365, thefirst scan trajectory 366 can extend generally along the Y axis, withsharp discontinuities 367B at each boundary 367A of adjacent dies 260.These discontinuities 367B are necessary to adjust the first scantrajectory 366 at these boundaries 367A so that the first stripe 364overlaps the existing pattern 233 printed on the dies 260 with a stepand repeat or step and scan lithography system. It should be noted thatin FIG. 3B, the new pattern 330 is transferred across nine dies 260 thatare aligned in a column. Thus, there are eight boundaries 367A and thefirst scan trajectory 366 includes eight discontinuities 367B.

In certain embodiments, in order to continuously transfer the firststripe 364, it may be necessary for the workpiece 22 to be moved slowlyduring the first scan 365 and/or for the system to be designed so thatthe exposure field 28 is has a Y axis dimension 328 that is relativelysmall. For example, in alternative, non-exclusive examples, the Y axisdimension 328 can be less than approximately 0.2, 1, 2, 3, 5, or 10millimeters.

After the first stripe 364 is created, the workpiece 22 can be steppedalong the X axis and subsequently scanned in the opposite direction tocreate the next stripe of parallel lines. The scanning processes andstepping processes are alternatively performed until the entire pattern330 of parallel lines 332 are created on the workpiece 22.

More specifically, FIG. 3C is a simplified illustration of the workpiece22 that includes a second stripe 368 (illustrated with short dashes) ofparallel lines 332 in addition to the first stripe 364 formed with theEUV lithography system 10 of FIG. 1A.

FIG. 3C also illustrates the rectangular shaped exposure field 28created by the EUV lithography system 10 of FIG. 1A on the workpiece 22.In this example, the second stripe 368 of parallel lines 332 weretransferred to the workpiece 22 during a second scan 369 of theworkpiece 22 relative to the exposure field 28. In the second scan 369,the stage assembly 20 (illustrated in FIG. 1A) is controlled to move theworkpiece 22 (upward in the drawing) relative to the exposure field 28along a second scan trajectory 370 (illustrated with a thicker, dashedline) to create the second stripe 368 of parallel lines 332. In FIG. 3B,the second scan trajectory 370 is jagged shaped and extends generallyparallel to the Y axis. More specifically, in the second scan 369, thesecond scan trajectory 370 is generally along the Y axis, but includessome movement along the X axis, and about the Z axis so that the newpattern 330 matches the existing pattern 233. As provided herein, themovement along the X axis and about the Z axis can be a function of theposition of the workpiece 22 along the Y axis. These adjustments willallow aligning the printed new pattern 330 to the average displacementof the existing pattern 233 in the X direction, and “steering” of thepatterning element lines 332 as they are printed across the diameter ofthe workpiece 22.

Additionally, as provided herein, the magnification of the patterningelement pattern 16A (illustrated in FIG. 1A) and the magnification tiltof the patterning element pattern 16A can be varied during the secondscan 369 so that the new pattern 330 more closely overlays the existingpattern 233 than if these adjustments were not made.

It should be noted that the second scan trajectory 370 is slightlydifferent from the first scan trajectory 366 because that distortion ofthe workpiece 22 is different in this area. As a result thereof, thesecond stripe 368 is slightly different from the first stripe 364.

Thus, as provided herein, the scan trajectory 366, 370 of the workpiece22 relative to the exposure field 28, the magnification and/ormagnification tilt can be varied for and during each scan 365, 369 totailor each stripe 364, 368 to more accurately overlay the existingpattern 233. Stated in another fashion, the scan trajectory 366, 370,the magnification, and the magnification tilt will be different fordifferent areas based on the amount of distortion of the existingpattern 233.

FIG. 3D is a simplified illustration of a portion of the first stripe364 that was transferred to the workpiece 22. In this Figure, a portionof the first scan trajectory 366 is illustrated with a thicker, dashedline and the leftmost line 332L and the rightmost line 332R areillustrated. In this embodiment, the first scan trajectory 366 isgenerally along the Y axis, but includes some movement along the X axis,and about the Z axis so that the new pattern 330 matches the existingpattern 233.

It should be noted that the first stripe 364 has a stripe width 372measured generally along the X axis between the lines 332L, 332R. Asprovided herein, the exposure apparatus 10 provided herein is controlledto selectively adjust the magnification of the patterning elementpattern 16A directed at the workpiece 22 to selectively adjust thestripe width 372 of the first stripe 364 along the scan trajectory 366during scanning so that the first stripe 364 matches the existingpattern 233. In FIG. 3D, the stripe width 372 decreases from top tobottom. However, the stripe width 372 can be varied in any fashion alongthe first scan trajectory 366 as needed so that the first stripe 364more accurately overlays the existing pattern 233 than without themagnification adjustment.

As non-exclusive examples, the adjustment of the focus position of thepatterning element 16 (illustrated in FIG. 1) or the workpiece 22 willcreate a magnification change that changes the stripe width 372 alongthe first scan trajectory 366. Using this effect, the patterning element16 and/or workpiece 22 can be moved slightly with the respective stageassembly in the focus direction (up or down along the Z axis) to makesmall changes in the pitch (selectively adjusting the pitch) of theprinted lines 332L, 332R. In another embodiment, the patterning elementpattern 16A (illustrated in FIG. 1A) can be selectively, mechanicallystretched or compressed along the X axis by the patterning element stageassembly 14 to change the magnification. Still alternatively, thetemperature of the patterning element 16 can be adjusted to mechanicallychange the pitch of the patterning element pattern 16A.

FIG. 3E is a simplified illustration of another portion of the firststripe 364 that was transferred to the workpiece 22. In this Figure, aportion of the first scan trajectory 366 is illustrated with a thicker,dashed line and the leftmost line 332L and the rightmost line 332R areagain illustrated. In this embodiment, the first scan trajectory 366 isagain generally along the Y axis, but includes some movement along the Xaxis, and about the Z axis so that the new pattern 330 more closelymatches the existing pattern 233 than if the scan trajectory was notadjusted.

It should be noted that the first stripe 364 has (i) a left intermediatewidth 374L measured generally along the X axis between the leftmost line332L and the scan trajectory 366, and (ii) a right intermediate width374R measured generally along the X axis between the rightmost line 332Rand the scan trajectory 366. As provided herein, the exposure apparatus10 provided herein is controlled to selectively adjust the magnificationtilt of the patterning element pattern 16A directed at the workpiece 22to selectively adjust the left intermediate width 374L and the rightintermediate width 374R during scanning so that the first stripe 364matches the existing pattern 233. In FIG. 3E, (i) the intermediatewidths 374L, 374R are approximately equal at the top, and (ii) the leftintermediate width 374L is greater than the right intermediate width374R near the bottom due to adjustments in the magnification tilt.However, the intermediate width 374L, 374R can be varied in any fashionalong the first scan trajectory 366 as needed so that the first stripe364 overlays the existing pattern 233.

As non-exclusive examples, the adjustment to the magnification tilt canbe achieved by rotating the patterning element pattern 16A about the Yaxis with the patterning element stage mover 14B (illustrated in FIG.1A) or rotating the workpiece 22 about the Y axis with the stageassembly 20 (illustrated in FIG. 1A). By tilting the patterning element16 and/or the workpiece 22 slightly about the Y axis, a “magnificationtilt” can be created where the printed pitch of the lines 332L, 332Rchanges linearly across the exposure field in the X direction. Forexample, the patterning element 16 can be rotated slightly in a firstdirection about the Y axis to decrease the left intermediate width 374L,and rotated slightly in an opposite, second direction about the Y axisto increase the left intermediate width 374L.

All of the adjustments provided herein will allow improved aligning ofthe printed new pattern 330 to the average displacement of the existingpattern 233 in the X direction, and “steering” of the patterning elementlines 332 as they are printed across the workpiece 22.

FIG. 3F is an enlarged, simplified illustration of a portion of theexisting pattern 233 (illustrated with small circles that representpoints on the existing pattern) and a portion of the first stripe 364 ofthe new pattern 330 that was transferred to the workpiece 22. FIG. 3Fillustrates how the first stripe 364 is tailored so that it closelyoverlaps the existing pattern 233. It should be noted that in the middleof each of the dies, the first stripe 364 closely overlays the existingpattern 233. However, at the boundaries 367A (one is highlighted with adashed oval) of adjacent dies 260 (two are illustrated with dashedlines) there can be some differences between the first stripe 364 andthe existing pattern 233 because of the rapid change at the boundary367A of adjacent dies 260.

A couple of alternative methods for controlling the EUV lithographysystem 10 are provided herein that allow the first stripe 364 to betterfollow the existing pattern 233 at the boundaries 367A.

For example, FIG. 4A is a simplified illustration of the workpiece 22that illustrates yet another first scan 465 of the workpiece 22 along afirst scan trajectory 466 past the exposure field 28. In thisembodiment, the extreme ultraviolet lithography system 10 (illustratedin FIG. 1A) is controlled so that every other die 260 (illustrated asdashed rectangles) in a die column 480 along the first scan trajectory466 is not exposed during the first scan 465. In this example, duringthe first scan 465, the workpiece 22 is moved so that nine dies 260 thatare aligned in a die column 480 along the Y axis pass under the exposurefield 28. It should be noted that these dies 260 were previouslycreated, and only one of the die columns 480 is illustrated in FIG. 4Afor clarity. Further, moving from the bottom to the top of the diecolumn 480, the dies 260 have been labelled 1-9 for ease of discussion.

In this example, the extreme ultraviolet lithography system 10 iscontrolled so that every odd numbered die 260 (e.g. dies 1, 3, 5, 7, 9)is exposed during the first scan 465 along the first scan trajectory 466to create a first portion 464F of the first stripe, and every evennumbered die 260 (e.g. dies 2, 4, 6, 8) is not exposed during the firstscan 465 along the first scan trajectory 466. With this design, thestage assembly 20 can be controlled during the first scan 465 to bettermatch the first portion 464F to the existing pattern 233 (illustrated inFIG. 2A) at the boundaries 467A of the odd numbered dies 260. Basically,during the first scan 465, the area of the even numbered dies 260provide time to move the workpiece 22 to the proper relative positionfor accurate printing of the next odd numbered die 260. In summary, inthe first scan 465, only the “odd number” dies 260 are exposed,interpolating a smooth trajectory while passing over the “even number”dies 260 with the exposure light turned off (and/or blocked by theshutter assembly 26 illustrated in FIG. 1A).

Subsequently, the extreme ultraviolet lithography system 10 iscontrolled to expose the unexposed dies along the first scan trajectory466 during a second scan 469. FIG. 4B is a simplified illustration ofthe workpiece 22 that illustrates the second scan 469 of the workpiece22 along a second first scan trajectory 470 past the exposure field 28.In this embodiment, the extreme ultraviolet lithography system 10(illustrated in FIG. 1A) is again controlled so that every other die 260(illustrated as dashed rectangles) in the die column 480 along thesecond scan trajectory 470 is not exposed during the second scan 469.

In this example, the extreme ultraviolet lithography system 10 iscontrolled so that every even numbered die 260 (e.g. dies 2, 4, 6, 8) isexposed during the second scan 469 along the second scan trajectory 470to create a second portion 464S of the first stripe, and every oddnumbered die 260 (e.g. dies 1, 3, 5, 7, 9) is not exposed during thesecond scan 469. With this design, the stage assembly 20 can becontrolled during the second scan 469 to better match the second portion464S to the existing pattern 233 at the boundaries 467A of the evennumbered dies 260. Basically, during the second scan 469, the area ofthe odd numbered dies 260 provide time to move the workpiece 22 to theproper relative position for printing of the next even numbered die 260.Thus, in the second pass over the same area, the even dies 260 areexposed using a smoothing interpolation while passing over the odd dies260 which have already been exposed.

It should be noted that the previously printed first portion 464F is notshown in FIG. 4B for clarity. However, with reference to FIGS. 4A and4B, the first portion 464F and the second portion 464S cooperate to forma complete first stripe of generally parallel lines. It should also benoted that the scan trajectories 466, 470 are partly overlapping but arenot exactly the same. With this design, the workpiece 22 must be scannedby the exposure field 28 two times to fully create the new pattern.

In certain embodiment, the shutter assembly 26 (illustrated in FIG. 1A)can be used to precisely start and stop exposure at the boundaries 467Aof the dies 260. In this embodiment, the shutter 26C is used toselectively define the Y axis edges of the exposure field 28. With thisdesign, the shutter 26C can be used to open and close in conjunctionwith scanning. More specifically, the shutter 26C can be controlled togradually close as the boundary 467A is being approached and close fullyat the boundary 467A. Subsequently, the shutter 26C can be controlled togradually open at the start of the next die 260. Alternatively, forexample, the EUV illumination source 34 can be turned on and off asnecessary to start and stop exposure.

With this design, the problem of distortion matching acontinuous-scanning exposure to layers printed with conventional toolswhich create discontinuities between adjacent shots is solved byscanning every stripe on the workpiece twice, exposing every other shotin the first pass, and the alternate shots in the second pass.

In yet another embodiment, with reference to FIG. 4C, if the workpiece22 is scanned at relatively low scanning velocity relative to theexposure field 28, and the stage assembly 20 (illustrated in FIG. 1A)has high acceleration capabilities, the exposure can be stopped at theboundary 467A of each die 260, and the workpiece 22 can be stopped andbacked up. Subsequently, the exposure can be started at the next die260. With this design, the EUV illumination system 10 illustrated inFIG. 1A is controlled to stop exposure at the interface 467A of adjacentdies 260 and reset the scan trajectory 492. In one embodiment, as theexposure field 28 reaches the interface 467A the shutter 26 begins toclose so that the adjacent die 260 is not exposed. Once the shutter isclosed and the exposure has stopped, the stage is decelerated andaccelerated in the opposite Y direction in a reverse movement. When thestage has reversed it's position enough, it is decelerated again andaccelerated in the scanning direction so that it is properly positionedwhen it again reaches the interface 467A. As the exposure field 28begins to pass the interface 467A, the EUV illumination system 10 iscontrolled to resume illumination and the shutter 26 begins to open.Thus, during the scan 490, the scan trajectory 492 (illustrated with asolid thick line) includes reverse movements along the Y axis duringexposure of the first stripe 494 (just the outer lines are illustratedwith dashed lines).

With this design, the problem of distortion matching acontinuous-scanning exposure to layers printed with conventional toolswhich create discontinuities between adjacent dies 260 is solved bystopping and resetting at each die 260. As a result thereof, the firststripe 494 and subsequent stripes will better overlay the existingpattern 233 at the boundaries 467A.

As described above, a photolithography system according to the abovedescribed embodiments can be built by assembling various subsystems,including each element listed in the appended claims, in such a mannerthat prescribed mechanical accuracy, electrical accuracy, and opticalaccuracy are maintained. In order to maintain the various accuracies,prior to and following assembly, every optical system is adjusted toachieve its optical accuracy. Similarly, every mechanical system andevery electrical system are adjusted to achieve their respectivemechanical and electrical accuracies. The process of assembling eachsubsystem into a photolithography system includes mechanical interfaces,electrical circuit wiring connections and air pressure plumbingconnections between each subsystem. Needless to say, there is also aprocess where each subsystem is assembled prior to assembling aphotolithography system from the various subsystems. Once aphotolithography system is assembled using the various subsystems, atotal adjustment is performed to make sure that accuracy is maintainedin the complete photolithography system. Additionally, it is desirableto manufacture an exposure system in a clean room where the temperatureand cleanliness are controlled.

Further, semiconductor devices can be fabricated using the abovedescribed systems, by the process shown generally in FIG. 5A. In step501 the device's function and performance characteristics are designed.Next, in step 502, a mask (reticle) having a pattern is designedaccording to the previous designing step, and in a parallel step 503 aworkpiece is made from a silicon material. The mask pattern designed instep 502 is exposed onto the workpiece from step 503 in step 504 by aphotolithography system described hereinabove in accordance with thepresent embodiment. In step 505 the semiconductor device is assembled(including the dicing process, bonding process and packaging process),finally, the device is then inspected in step 506.

FIG. 5B illustrates a detailed flowchart example of the above-mentionedstep 504 in the case of fabricating semiconductor devices. In FIG. 5B,in step 511 (oxidation step), the workpiece surface is oxidized. In step512 (CVD step), an insulation film is formed on the workpiece surface.In step 513 (electrode formation step), electrodes are formed on theworkpiece by vapor deposition. In step 514 (ion implantation step), ionsare implanted in the workpiece. The above mentioned steps 511-514 formthe preprocessing steps for workpieces during workpiece processing, andselection is made at each step according to processing requirements.

At each stage of workpiece processing, when the above-mentionedpreprocessing steps have been completed, the following post-processingsteps are implemented. During post-processing, first, in step 515(photoresist formation step), photoresist is applied to a workpiece.Next, in step 516 (exposure step), the above-mentioned exposure deviceis used to transfer the circuit pattern of a mask (reticle) to aworkpiece. Then in step 517 (developing step), the exposed workpiece isdeveloped, and in step 518 (etching step), parts other than residualphotoresist (exposed material surface) are removed by etching. In step519 (photoresist removal step), unnecessary photoresist remaining afteretching is removed.

Multiple circuit patterns are formed by repetition of thesepreprocessing and post-processing steps.

While the assembly as shown and disclosed herein is fully capable ofobtaining the objects and providing the advantages herein before stated,it is to be understood that it is merely illustrative of the presentlypreferred embodiments and that no limitations are intended to thedetails of construction or design herein shown other than as describedin the appended claims.

What is claimed is:
 1. An extreme ultraviolet lithography system thattransfers a pattern of parallel lines onto a workpiece that includes anexisting pattern, the lithography system comprising: a workpiece stageassembly that retains and moves the workpiece; an EUV illuminationsystem that directs an extreme ultraviolet beam at a patterning elementthat defines the pattern of parallel lines; a projection opticalassembly that projects and transfers an image of the the plurality ofparallel lines, within an exposure field, onto the workpiece as theworkpiece is moved relative to the exposure field during a first scan,the exposure resulting in a first stripe of the imaged plurality oflines extending generally along a first axis; and a control system thatcontrols the workpiece stage assembly to move the workpiece relative tothe exposure field along a first scan trajectory that is generally alongthe first axis during the first scan; wherein the control systemselectively adjusts a control parameter during the first scan of theworkpiece stage assembly so that the first stripe of parallel linesbecomes distorted so as to overlay and more accurately match adistortion of the portion of existing pattern positioned under the firststripe of parallel lines relative to if the control parameter is notadjusted.
 2. The extreme ultraviolet lithography system of claim 1wherein the control parameter includes selectively adjusting the firstscan trajectory to include some movement along a second axis that isorthogonal to the first axis during the first scan so that the firststripe of parallel lines more accurately overlays the portion ofexisting pattern positioned under the first stripe of parallel linesrelative to if the movement along the second axis is not performed. 3.The extreme ultraviolet lithography system of claim 2 wherein thecontrol parameter includes selectively adjusting the first scantrajectory to include some movement about a third axis that isorthogonal to the first and second axes during the first scan so thatthe first stripe of parallel lines more accurately overlays the portionof existing pattern positioned under the first stripe of parallel lines.4. The extreme ultraviolet lithography system of claim 3 wherein duringthe first scan, the movement along the second axis or about the thirdaxis is a function of a workpiece position of the workpiece along thefirst axis relative to if the movement along the second axis or aboutthe third axis is not performed.
 5. The extreme ultraviolet lithographysystem of claim 1 wherein the control parameter includes selectivelyadjusting a magnification of the plurality of parallel lines during thefirst scan so that the first stripe of parallel lines more accuratelyoverlays the portion of existing pattern positioned under the firststripe of parallel lines relative to if the magnification is notadjusted.
 6. The extreme ultraviolet lithography system of claim 1wherein the control parameter includes selectively adjusting amagnification tilt of the plurality of parallel lines during the firstscan so that the first stripe of parallel lines more accurately overlaysthe portion of existing pattern positioned under the first stripe ofparallel lines.
 7. The extreme ultraviolet lithography system of claim 1wherein the control parameter includes selectively adjusting one or moreof (i) the first scan trajectory to include some movement along a secondaxis that is orthogonal to the first axis, and some movement about athird axis that is orthogonal to the first and second axes during thefirst scan; (ii) a magnification of the patterning element patternduring the first scan; and (iii) a magnification tilt of the patterningelement pattern during the first scan.
 8. An extreme ultravioletlithography system that transfers a pattern of parallel lines onto aworkpiece that includes an existing pattern, the existing patternincluding a plurality of dies, the lithography system comprising: aworkpiece stage assembly that retains and moves the workpiece; an EUVillumination system that directs an extreme ultraviolet beam at apatterning element that defines the pattern of parallel lines; aprojection optical assembly that projects and transfers an image of theplurality of parallel lines, within an exposure field, onto theworkpiece as the workpiece is moved relative to the exposure fieldduring a first scan, the exposure resulting in a first stripe of theimaged plurality of lines extending generally along a first axis; and acontrol system that controls the workpiece stage assembly to move theworkpiece relative to the exposure field along a first scan trajectorythat is generally along the first axis during the first scan; whereinthe control system selectively adjusts a control parameter during thefirst scan of the workpiece stage assembly so that the first stripe ofparallel lines overlays and more accurately matches the portion ofexisting pattern positioned under the first stripe of parallel linesrelative to if the control parameter is not adjusted; and wherein thecontrol system controls the EUV illumination system so that every otherdie along the first scan trajectory is not exposed during the firstscan.
 9. The extreme ultraviolet lithography system of claim 8 whereinthe control system controls the EUV illumination system to expose theunexposed dies along the first scan trajectory during a second scan. 10.The extreme ultraviolet lithography system of claim 1 wherein theexisting pattern includes a plurality of dies, wherein the controlsystem stops exposure at an interface of adjacent dies; and wherein thecontrol system controls the workpiece stage assembly to move the stagein a manner that resets the first scan trajectory so that the newpattern overlays the existing pattern during exposure of the subsequentdie.
 11. The extreme ultraviolet lithography system of claim 10 whereinthe EUV illumination is stopped by a shutter assembly located at or neara plane that is optically conjugate to the workpiece.
 12. The extremeultraviolet lithography system of claim 10 wherein the workpiece stageassembly resets the first scan trajectory by: decelerating the stage tostop the scanning motion; accelerating the stage in the oppositedirection; decelerating the stage to stop the reverse motion;accelerating the stage to resume scanning.
 13. The extreme ultravioletlithography system of claim 1 wherein the control system selectivelyadjusts the first scan trajectory and a pitch of the parallel linestransferred to the workpiece during the first scan so that the firststripe of parallel lines are distorted to overlay the portion ofexisting pattern positioned under the first stripe of parallel lines.14. A method for transferring a pattern having a plurality of parallellines onto a workpiece that includes an existing pattern that isdistorted comprising: providing a patterning element having a patterningelement pattern; moving the workpiece with a workpiece stage moverassembly; directing an extreme ultraviolet beam at the patterningelement with an EUV illumination system; imaging the patterning elementpattern onto the workpiece using a projection optical assembly, therebycreating the plurality of parallel lines on the workpiece when theworkpiece is moved relative to the exposure field during a first scan, afirst stripe of parallel lines extending generally along a first axis;and controlling the workpiece stage assembly with a control system tomove the workpiece relative to the exposure field along a first scantrajectory that is generally along the first axis during the first scan;wherein the control system selectively adjusts a control parameterduring the first scan so that the first stripe of parallel lines becomesdistorted so as to overlay and match the distortion of the portion ofexisting pattern positioned under the first stripe of parallel linesmore accurately than if the control parameter were not adjusted.
 15. Themethod of claim 14 wherein the step of controlling includes controllingthe workpiece stage assembly so that the first scan trajectory includessome movement along a second axis that is orthogonal to the first axisduring the first scan so that the first stripe of parallel lines moreaccurately overlays the portion of existing pattern positioned under thefirst stripe of parallel lines.
 16. The method of claim 15 wherein thestep of controlling includes controlling the workpiece stage assembly sothat the first scan trajectory includes some movement about a third axisthat is orthogonal to the first and second axes during the first scan sothat the first stripe of parallel lines more accurately overlays theportion of existing pattern positioned under the first stripe ofparallel lines.
 17. The method of claim 16 wherein the control parameterincludes selectively adjusting a magnification of the patterning elementpattern during the first scan so that the first stripe of parallel linesmore accurately overlays the portion of existing pattern positionedunder the first stripe of parallel lines.
 18. The method of claim 14wherein the control parameter includes selectively adjusting amagnification tilt of the patterning element pattern during the firstscan so that the first stripe of parallel lines more accurately overlaysthe portion of existing pattern positioned under the first stripe ofparallel lines.
 19. The method of claim 14 wherein controlling includesselectively adjusting at least one of (i) the first scan trajectory toinclude some movement along a second axis that is orthogonal to thefirst axis, and/or some movement about a third axis that is orthogonalto the first and second axes during the first scan; (ii) a magnificationof the patterning element pattern during the first scan; and (iii) amagnification tilt of the patterning element pattern during the firstscan.
 20. The method of claim 14 wherein the existing pattern includes aplurality of dies, and wherein controlling includes controlling the EUVillumination system so that every other die along the first scantrajectory is not exposed during the first scan.
 21. The method of claim20 further comprising controlling the EUV illumination system to exposethe unexposed dies along the first scan trajectory during a second scan.22. The method of claim 14 wherein the existing pattern includes aplurality of dies, and wherein the method includes controlling the EUVillumination system with the control system to stop at an interface ofadjacent dies and reset the first scan trajectory.
 23. The method ofclaim 14 including selectively adjusting the first scan trajectory and apitch of the parallel lines transferred to the workpiece during thefirst scan with the control system so that the first stripe of parallellines are distorted to overlay the portion of existing patternpositioned under the first stripe of parallel lines.